As a detecting device for a terahertz wave, there have been known a thermal type detection element and a quantum type detection element up to now. Examples of the thermal type detection element include a microbolometer (a-Si, VOx, etc.), a pyroelectric element (LiTaO3, TGS, etc.), and a Golay cell. Such a thermal type detection element converts a physical change caused by energy of an electromagnetic wave into heat, and then converts a temperature change into a thermoelectromotive force or a resistance for detection. Cooling is not always required, but a response is relatively slow because heat exchange is used. Examples of the quantum type detection element include an intrinsic semiconductor element (MCT (HgCdTe) photoconductive element, etc.) and a quantum well infrared photodetector (QWIP). This quantum type detection element captures the electromagnetic wave as photons, and then detects a photovoltaic power or resistance change of a semiconductor having a small band gap. The response is relatively fast, but cooling is required because a thermal energy of a room temperature in such a frequency range cannot be ignored.
As a detecting device which has a relatively fast response and which does not require cooling, a detecting device for a terahertz wave which uses a diode element is under development. The detecting device captures an electromagnetic wave as a high frequency electric signal, and the diode element rectifies and detects the high frequency electric signal received by an antenna or the like. Patent Literature 1 discloses such a detecting device. In the detecting device disclosed in Patent Literature 1, the diode element is a Schottky barrier diode and detects an electromagnetic wave of about 28 THz (having a wavelength of 10.6 μm) emitted by a CO2 laser with use of a top antenna and a substrate as a ground as two electrode.
On the other hand, other than a vertical type Schottky barrier diode in which two electrodes are vertically placed with respect to a substrate, there has conventionally been known a lateral type Schottky barrier diode in which two electrodes are placed on a surface of a substrate. Patent Literature 2 discloses such a diode element. The element described in Patent Literature 2 includes a guard ring along a circumference of a Schottky electrode for the purpose of enhancing resistance to reverse bias.